In order to expand market opportunities, manufacturers of tobacco related products have increasingly begun to develop attractive specialty items to attract customers. Among these specialty items are cigarettes having brown wrappers. Brown wrappers are considered to impart a natural, earthy image and provide a cigarette wrapper having the appearance of tobacco. In order to obtain the desired brown color, it has been common to utilize FDA approved dyes and other artificial colorants. However, since some artificial colorants and dyes have been alleged to have detrimental health effects, some cigarette manufacturers have opted for natural colorants to avoid potential toxicological problems and to further promote the natural image.
It is well-known in the art to use natural colorants to color cigarette paper. Most of the prior art uses disclose the addition of natural colorants, such as caramel, chocolate and licorice, to the paper by impregnating, spraying, soaking or otherwise coating the paper with the colorant. One such attempt is taught by U.S. Pat. No. 4,146,041 which teaches a brown cigarette wrapper produced by staining conventional paper with humic acids or salts and then washing the paper with water to reduce the concentration of residual alkaline metal salts. However, such methods often have several disadvantages. For example, to produce a sufficiently dark wrapper, it is, depending upon the colorant, often necessary to use large amounts of the colorant. Adding too much colorant may have detrimental effects, such as reducing the porosity of the paper and thereby reducing the burn rate of the paper, producing unpleasant odors and increased smoke, and especially in the case of caramel, making the wrapper sticky or otherwise unappealing.
It is also known in the art to add colorants to the liquids slurry or furnish from which the paper is produced. One such method is to treat the furnish with iron (ferric) oxide. However, to obtain sufficiently dark results with this method, it is often necessary to use large amounts (in excess of 2% by weight of paper) of ferric oxide. Paper treated with such large amounts of ferric oxide is undesirable since the paper produces an undesirable rust colored ash when burned. This range of acceptable percentages is dependent upon several factors. Certain tipping papers, used for the cigarette tip which is not burned, may have between 6 and 8% of an iron oxide colorant. The upper limit of iron oxide may be as high as 1.5-2% in paper that will be burned, although at levels as low as 1% by weight the potential for red ash exists. The formation of a red ash may be ameliorated by the addition of caramel, licorice and other natural colorants. Also, the tobacco blend itself may reduce the formation of red ash. Additionally, ferric oxide gives the paper a flat, undesirable color when it is the only colorant used.
Therefore a need exists for a method by which cigarette paper can be treated with natural colorants to provide it with a sufficiently dark appearance without detracting from its function or appeal.